During a true “unstabilized approach” scenario, pilots are almost always trying to get back on a proper approach path. So, if the aircraft is “too high”, the pilot dives the aircraft to intercept a proper glideslope (often 3 degrees). This means if the proper glideslope is three degrees and the aircraft is way above the glideslope (“too high” scenario), the aircraft will be flown at greater than a 3° flight path angle to descend and intercept the 3° glideslope.
In an existing stabilized approach monitor (SAM) such as that produced by Honeywell International, Inc., when a pilot is intending to land on a temporarily displaced threshold (often due to construction), the SAM issues a “Too High” alert on a perfectly stabilized approach. This is because the SAM is not aware of a temporary displaced threshold. Therefore, the aircraft appears to be too high with respect to the predefined glideslope to the runway threshold stored in the runway database. Therefore, the alert is a nuisance because the aircraft is on a stabilized approach to the displaced threshold.